The present invention relates to a powered zoom camera, and in particular to a powered zoom camera in which the ratio of the dimension of the image of a main object on a focal plane to the dimension of a frame can be automatically kept constant merely by tracking the object.
Although several ratios of the dimension of the image of a person on a focal plane to the dimension of a photographic frame will suffice when a photographer takes a portrait by using a zoom lens, he or she changes the zoom position by manipulating a zoom ring with the fingers or by pressing zoom buttons every time. If a moving object is photographed, for example, if a sliding form or a person skiing is photographed, it is very hard work to track with a zoom lens the object which approaches toward or moves away from the photographer at high speed.
A camera having an automatic zooming function in which the ratio of the size of the image of a person on a focal plane to the size of a photographic frame can be preliminarily preset by a photographer has been proposed in the Japanese Laid-Open Patent Applications Nos. Sho/62-95959 and Sho/63-220118 by the present assignee.
Such a powered zoom camera enables a photographer to take a desired picture only by moves away an object without paying attention to zoom operation. Since the zooming speed in the automatic zoom mode is the same as that in the manual zoom mode and since zooming can not follow a fast moving object, there is a possibility of losing a shutter chance. That is, zooming speed can be increased to any high speed since zooming should only be conducted until the preliminarily preset ratio of the size of the image of an object on a focal plane to the size of the frame is obtained. In the proposed powered zoom camera, the zooming speed is not changed. Accordingly, the zooming speed in the automatic zoom mode is as slow as that in the manual zoom mode.
Although it is necessary to appropriately change the ratio of the dimension of an object image on a focal plane to the dimension of the frame in the automatic zoom mode, manual zoom operation by manual zoom switches are not necessary in the automatic zoom mode. Accordingly it is preferable that the manual zoom switches be used as a means for changing the ratio of the dimension of an object to that of a frame.